Outline

Background and aim: Despite the well-known risk of acute agranulocytosis, ambulatory prescriptions of metamizole raised from 32.2 Mio. Defined Daily Doses (DDD) in 2000 to 85.8 Mio. DDD in 2007 (+166%). The total number of German adult patients with metamizole induced agranulocytosis leading to hospitalisation or occurring in the hospital has not been estimated so far.

Material and method: Within PVZ-FAKOS, a German National Pharmacovigilance Center in Berlin, hospitalised patients with acute agranulocytosis in Berlin were identified. WHO causality assessment was used to identify cases caused by metamizole. We estimated the total number of patients with metamizole induced agranulocytosis in Germany under the assumption of 100% case ascertainment and similar metamizole prescription habits as in whole Germany.

Results: 92 patients with a validated diagnosis of AGR were included from Oct 2000 to June 2009 with 27 of them (29.3%) attributed to metamizole. The total numbers of adults with metamizole induced agranulocytosis in Germany were estimated as approx. N=633 during the total study period (95% confidence interval [CI] 417–921) or N=72 per year (95% CI 48–105).

Conclusions: Even with the conservative assumption of complete case ascertainment in Berlin, a substantial number of patients were affected by metamizole induced agranulocytosis during the last years in Germany. Given the potential fatal consequences of agranulocytosis, these estimates support concerns about the increasing ambulatory use of metamizole in Germany.

Acknowledgements: PVZ-FAKOS is being funded by the Federal Institute for Drugs and Medical Devices, Germany